Conventional processes for the acylation of aromatic compounds, in particular the ethers of phenols consist of carrying out a Friedel-Crafts acylation reaction. The aromatic compound is reacted with an acylation agent in the presence of aluminium chloride
The inherent disadvantages in the use of conventional Lewis acid metal chlorides for Friedel-Crafts acylation are that they are non-regenerable and require more than stoichiometric amounts because of strong complexation with the carbonyl product formed. Work-up to decompose the resultant intermediate complex by hydrolysis forms a large amount of waste product and separation of the product involves lengthy, cumbersome and expensive procedure.
Reference may be made to a publication by Choudary et al., Applied Catalysis A; 171,159, 1998 wherein aromatic ethers are acylated with acid anhydrides in the presence of metal ion exchanged clays with moderate yields. The drawbacks are that the conversions are moderate with low space time yields.
Reference may be made to a U.S. Pat. No. 4,960,943 wherein a process for the acylation of anisole with acid anhydrides in the presence of zeolite catalysts is disclosed. The drawbacks in this process are moderate yields and the reaction is carried out at high temperatures and pressures.
Reference may be made to a publication by Gaare et al. Journal of Molecular Catalysis, 109, 177, 1996 wherein anisole is acylated by acetyl chloride and acetic anhydride by modified zeolites.
Reference may be made to a U.S. Pat. No. 5,817,878 wherein substituted aromatic ethers, in particular anisole is acylated with an acylating agent in the presence of zeolite beta catalyst.
Reference may be made to a U.S. Pat. No. 6,013,840 wherein substituted aromatic ethers, in particular veratrole and anisole are acylated with an acylating agent in the presence of a Y zeolite, dealuminated and metal exchanged Y zeolite and H.sup.+ -zcolite beta catalyst.
Although the above inventions afforded good selectivity and activity, the object of the present invention is to devise a catalyst of enhanced activity and higher space time yields to reduce the capital and operative costs.